For anyone interested in making my Singled Ended Ultralinear amplifier, Antique Electronic Supply is now carrying the EL156 output tube. Price is a bit higher than a Chinese supplier, but at least you can try to return the tube if you have a problem with it.
I've been buying from Antique since 1990 and continue to do so because of their great customer service. Plus this year for Christmas they sent me a small tin of mints shaped like a 2A3! Of course Front Panel Express sent me some chocolate shaped like a laser cut panel. I guess being a 'big spender' has its perks. Heh.